Detection Of Catechol Research Articles

Biosensor based on MXene-Y2O3 composite for ultrasensitive detection of catechol in water samples

Biosensor based on MXene-Y2O3 composite for ultrasensitive detection of catechol in water samples

Simultaneous Determination of Phenolic Pollutants based on Electrochemical Oxidation by Nanoporous Gold

Abstract Phenolic compounds, as highly toxic pollutants, can cause great harm to human beings and the environment even at very low concentrations. Therefore, the simultaneous detection of multiple phenolic pollutants is critically valuable for environmental monitoring. Here, an electrochemical sensor based on a glassy carbon electrode (GCE) modified by nanoporous gold (NPG) was successfully developed for the determination of phenolic pollutants including phenol (Ph), hydroquinone (HQ), catechol (CT), and o-nitrophenol (ONP), which realized not only the sensitive individual detection of each phenolic pollutant but also the sensitive simultaneous detection of these four phenolic pollutants. For the simultaneous detection, the limits of detection of Ph, HQ, CT, and ONP were 0.85, 0.17, 0.19, and 1.30 μM as well as the sensitivities of 0.24, 1.17, 1.08, and 0.16 μA μM−1 cm−2, respectively. Additionally, the NPG/GCE electrochemical sensor exhibited good stability and anti-interference capability. The recovery rates of Ph, HQ, CT, and ONP in seawater samples and wastewater samples ranged from 94.64% to 105.87%. These results indicated that the prepared NPG/GCE electrochemical sensor may be an ideal choice for the reliable simultaneous detection of multiple phenolic pollutants.

Two-Dimensional TiS2 Nanosheet- and Conjugated Polymer Nanoparticle-Based Composites for Sensing Applications.

The assessment of phenolic compounds in food samples, environmental samples, and medical applications has gained importance recently. Here, we present research on novel conjugated polymer nanoparticles (P-PimBzBt NPs) and their composites with two-dimensional titanium disulfide nanosheets (2D-TiS2) for electrochemical tyrosinase (TYR)-based catechol detection. P-PimBzBt NPs are decorated with 2D-TiS2 to enhance the electrochemical performance for biosensing. In addition, the interaction of P-PimBzBt NPs with TiS2 was investigated at the molecular level by employing van der Waals (vdW) dispersion-corrected density functional theory (DFT) calculations and classical all-atom molecular dynamics simulations. According to the theoretical studies, the presence of the TiS2 layer increases the interfacial interaction with the conjugated polymer via electrostatic interactions. Using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) analyses, the production of SPE/TiS2@P-PimBzBt NPs/TYR nanobiosensors was examined. With a detection range of 3.0-27.5 μM, 0.33 μM LOD, and 3.89 μA/μM·cm2 sensitivity values, the sensing layer based on the TiS2@P-PimBzBt NP composites has a targeting ability toward catechol. Its selectivity was investigated using commonly used interfering ions and compounds such as citric acid, urea, glucose, uric acid, KCl, and NaCl. Application of nanobiosensors to actual samples (tap water and black tea) was carried out with high accuracy. The fabricated biosensing platform demonstrates that P-PimBzBt NPs with 2D-TiS2 nanomaterial functionalization are appropriate as electrode materials and could be used to create an inexpensive, fast-response, and highly selective electrochemical biosensor for the detection of catechol in actual samples.

Simultaneous Electrochemical Detection of Catechol and Hydroquinone Based on a Carbon Nanotube Paste Electrode Modified with Electro-Reduced Graphene Oxide.

Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4-400 μM with a detection limit of 0.083 μM for CC and 0.028 μM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects.

Conductive Carbon from Taro Stems for Simultaneous Detection of Hydroquinone and Catechol

Conductive Carbon from Taro Stems for Simultaneous Detection of Hydroquinone and Catechol

Simultaneous electrochemical detection of hydroquinone and catechol using a carbon nanotube paste electrode modified with electrochemically polymerized L-alanine

Simultaneous electrochemical detection of hydroquinone and catechol using a carbon nanotube paste electrode modified with electrochemically polymerized L-alanine

A stable and efficient electrochemical sensor for hydroquinone and catechol detection in real-world water samples using mesoporous CaM@rGO nanocomposite

Hydroquinone (HQ) and catechol (CC) are widespread environmental pollutants known for their high toxicity and poor biodegradability. Herein, we devised an electrochemical sensor for sensitive and selective detection of HQ and CC. The glassy carbon electrode (GCE) was meticulously modified by using the Ca-perovskite (CaTiO3/GCE), zinc-based metal-organic frameworks (Zn-MOF/GCE), and their nanocomposite with reduced graphene oxide (rGO), i.e., CaTiO3-Zn-MoF@rGO/GCE (CaM@rGO/GCE). The CaM@rGO/GCE sensor showed stupendous electrochemical performance due to the synergistic effects of rGO's high conductivity and Ca-perovskite's electrocatalytic activity. Furthermore, the Zn-MOF component ensures the sensor's remarkable stability. The developed sensor boasts impressive selectivity towards HQ and CC, achieving exceptionally low detection limits (0.0086 µM (S/N = 3) for HQ, 0.0115 µM (S/N = 3) for CC), and broad linear ranges (0.05–105 µM for HQ, 0.05–120 µM for CC). The sensor shows better sensitivity to hydroquinone (HQ) than catechol (CC) due to the absence of intramolecular hydrogen bonding in HQ. The sensor's real-world applicability was validated by analyzing environmental water samples, demonstrating its immense potential for practical environmental monitoring.

Development of novel electrochemical sensor based on Co-Fe layered double hydroxide for simultaneous determination of Hydroquinone, Catechol, and Resorcinol

In this work, a novel electrochemical sensor was developed using a glassy carbon electrode modified with Co-Fe-layered double hydroxides (Co/Fe-LDH/GCE) for the detection of dihydroxybenzene isomers (Hydroquinone (HQ), Catechol (CC), and Resorcinol (RS) due to the large active surface area, facile electronic transport, and high electrocatalytic activity features of LDH. X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDX), and scanning electron microscopy (SEM) techniques were used to characterize the modifier. Under the optimized conditions, the differential pulse voltammetry (DPV) method was used as a sensitive and efficient method to measure dihydroxybenzene isomers. Well-separated oxidation peak potentials corresponding to HQ, CC, and RS were observed at 0.04 V, 0.150 V, and 0.560 V, respectively. The linear range was 2.5 × 10−9 to 1.2 × 10−5 M for hydroquinone and catechol and 7.5 × 10−9 to 4.2 × 10−6 M for resorcinol, with a detection limit of 0.001, 0.001, and 0.005 µM (S/N=3) for hydroquinone, catechol, and resorcinol, respectively. The Co/Fe-LDH sensor demonstrated a fast response, high sensitivity, excellent stability, and satisfactory repeatability. The modified electrode was successfully applied to the direct determination of DBIs in river water, providing reliable recovery data.

A smartphone-based tunable tyrosinase functional mimic modulated portable amperometric sensor for the rapid and real-time monitoring of catechol

A smartphone-based electrochemical sensor for rapid detection of catechol (CC) was designed. The system contained a smartphone, a hand-held detector, and tyrosinase enzyme mimicking material modified screen-printed carbon electrode (SPCE). Metal nanoparticles confined in porous carbon have been widely used as enzyme mimics owing to their enhanced electrochemical activity. However, the fabrication of enzyme-mimicking catalysts in a scalable and tunable manner is challenging. A two-step synthesis strategy was followed: carbonization of the silica template to form cubic-structured mesoporous carbon (CMC) and high-temperature calcination for copper confinement into CMC (Cu–CMC). The non-covalent interactions enable the Cu precursors to coordinate with the carbon atoms in the face-centered cubic lattice of CMC. The uncalcined material is the as-synthesized (As–Cu–CMC), while the 900 °C calcined are stage 1 (Cu–CMCS1) and stage 2 (Cu–CMCS2) materials with different Cu loadings. The Cu–CMCS2 possess a large pore volume (0.224 cm3g−1) and high surface area (104.2 m2/g). The Cu–CMCS2 modulated sensors enable rapid and real-time detection of CC. Under optimized conditions, the linear range of 1.0–1000 µM (0.0 V vs. integrated Ag/AgCl reference electrode) with the sensitivity and lower detection limit of 10.21 µA µM−1 cm−2 and 0.099 μM (S/N=3) was achieved. The excellent sensor performance is attributed to the increased number of Cu vacancies that mimic the native tyrosinase enzyme. The sensor connected to a portable potentiostat enable high-throughput real-time testing of the CC without sophisticated equipment. Furthermore, the sensor detected CC in green tea and water samples, and the results were validated using UV–visible spectrophotometry and high-performance liquid chromatography.Abbreviations: CMC, cubic-structured mesoporous carbon; Cu–CMCS2, copper loaded stage 2 material; CC, catechol; CMS, cubic mesoporous silica; SPCE, screen-printed carbon electrode; HF, hydrofluoric acid; P123, Pluronic 123; TEOS, Tetraethyl orthosilicate; AA, ascorbic acid; Glu, glucose; HQ, hydroquinone; 4-NP, 4-nitrophenol; CA, caffeic acid; RS, resorcinol; Cu–CMCS1, copper loaded stage 1 material; UV–Vis, UV–visible spectrophotometry; FE-SEM, field-–emission scanning electron microscopy; EDS, energy–dispersive X–-ray spectroscopy; Si, silica; TEM, transmission electron microscopy; NPs, nanoparticles; SAED, selected area electron diffraction; FT-IR, Fourier-Transform Infrared Spectroscopy; BET, Brunauer–Emmett–Teller; BJH, Barrett–Joyner–Halenda; TGA, Thermogravimetric analysis; CV, cyclic voltammetry; ipa, anodic peak current; ECSA, electrochemically active surface area; EIS, electrochemical impedance spectroscopy; Rct, charge-transfer resistance; CA, chronoamperometry; LOD, limit of detection.

Electrochemical sensing platform using reduced graphene oxide and Sn MOF-derived hollow cubic composites for sensitive detection of catechol in environmental water samples

Catechol, a polyphenolic molecule and significant organic chemical intermediate, is a highly dangerous environmental contaminant due to its unpredictable nature and potential harm to both humans and the environment. This study presents the development of Sn MOF@rGO-650, identified as a hollow cube by SEM and TEM, created by carbonizing rGO on the surface of Sn MOF after in situ encapsulation. The Sn MOF@rGO-650 modified glassy carbon electrode was successfully constructed for the electrochemical detection of catechol. Under optimal conditions, the sensor exhibited a detection limit of 33 nM, a linear range of 0.20 μM–28 μM, and good long-term stability and reproducibility. This work proves for the first time that Sn MOF@rGO-650 composites can effectively detect catechol in real environmental water samples, achieving recoveries between 95.7 % and 104.8 %, and is validated in UV spectroscopy, which highlights its potential for practical applications.

Red-emitting 4-methyl coumarin fused barbituric acid as an electrochemical sensor for catechol detection and probe for latent fingerprints.

Herein, we have reported a red-emitting 4-methyl coumarin fused barbituric acid azo dye (4-MCBA) synthesized byconventional method. Density functional theory (DFT) studies of tautomer compounds were done using (B3LYP) with a basis set of 6-31G(d,p). NLO analysis has shown that tautomer has mean first-order hyperpolarisabilities (β) value of 1.8188 × 10-30 esu and 1.0470 × 10-30esu for azo and hydrazone forms, respectively, which is approximately nine and five times greater than the magnitude of urea. 4-MCBA exhibited two absorption peaks in the range of 290-317 and 379-394 nm, and emission spectra were observed at 536 nm. CV study demonstrated that the modified 4-MCBA/MGC electrode exhibited excellent electrochemical sensitivity towards the detection of catechol and the detection limit is 9.39 μM under optimum conditions. The 4-MCBA employed as a fluorescent probe for the visualisation of LFPs on various surfaces exhibited Level-I to level-II LFPs, with low background interference.

Simultaneous electrochemical detection of hydroquinone and catechol using flexible laser-induced metal-polymer composite electrodes

The conversion of waste polymers into functional materials presents a promising approach for PET upcycling. In this study, we exploit PET transformed into a Laser-Induced Graphene/Al NPs/PET nanocomposite (LIMPc − Laser-Induced Metal-Polymer composite) modified with electrodeposited gold nanoparticles (AuNPs). The morphology and structure of the material were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The nanocomposite was employed as a flexible electrochemical sensor for the simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CT). The LIMPc-plasma-NaOH-Au composite displayed well-defined oxidation peaks for HQ and CT during electrochemical analysis, with limits of detection (LOD) as low as 47 nM for CT and 56 nM for HQ, within a linear range of 0.1–300 μM for both compounds. The long-term stability of LIMPc-plasma-NaOH-Au and its performance in real sample analysis demonstrate its potential for environmental monitoring applications.

Novel Schiff's base-assisted synthesis of metal-ligand nanostructures for multi-functional applications: Detection of catecholamines/antibiotics, removal of tetracycline, and antifungal treatment against plant pathogens

The development of nanozymes (NZ) for the simultaneous detection of multiple target chemicals is gaining paramount attention in the field of food and health sciences, and waste management industries. Nanozymes (NZ) effectively compensate for the environmental vulnerability of natural enzymes. Considering the development gap of NZ with diverse applications, we synthesized versatile Schiff’s base ligands following a facile route and readily available starting reagents (glutaraldehyde, aminopyridines). DPDI, one of the synthesized ligands, readily reacted with transition metal ions (Cu+2, Ag+1, Zn+2 in specific) under ambient conditions, yielding the corresponding nanoparticles/MOF. The structures of ligands and their products were confirmed using various analytical techniques. The enzymatic efficacy of DPDI-Cu (km 0.25 mM=, Vmax = 10.75 µM/sec) surpassed Tremetese versicolor laccase efficacy (km 0. 5 mM=, Vmax = 2.15 µM/sec). Additionally, DPDI-Cu proved resilient to changing pH, temperature, ionic strength, organic solvent, and storage time compared to laccase and provided reusability. DPDI-Cu proved promising for colorimetric detection of dopamine, epinephrine, catechol, tetracycline, and quercetin. The mechanism of oxidative detection of TC was studied through LC/MS analysis. DPDI-Cu-bentonite composite efficiently adsorbed tetracycline with maximum Langmuir adsorption of 208 mg/g. Moreover, DPDI/Cu and DPDI-Ag nanoparticles possessed antifungal activity exhibiting a minimum inhibitory concentration of 400 µg/mL and 3.12 µg/mL against Aspergillus flavus. Florescent dye tracking and SEM/TEM analysis confirmed that DPDI-Ag caused disruption of the plasma membrane and triggered ROS generation and apoptosis-like death in fungal cells. The DPDI-Ag coating treatment of wheat seeds confirmed the non-phytotoxicity of Ag-NPs.

Cu Single Atoms Embedded in N-Doped Hollow Carbon Spheres for Simultaneous Electrochemical Detection of Hydroquinone and Catechol

Cu Single Atoms Embedded in N-Doped Hollow Carbon Spheres for Simultaneous Electrochemical Detection of Hydroquinone and Catechol

Binary-amplifying electrochemiluminescence sensor for sensitive assay of catechol and luteolin based on HKUST-1 derived CuO nanoneedles as a novel luminophore

Herein, a highly novel and effective electrochemiluminescence (ECL) sensor based on metal-organic framework (MOF, HKUST-1) derived CuO nanoneedles (HKUST-1 derived CuO NNs), gold nanoparticles (AuNPs) and TiO2 was developed for ultrasensitive detection of catechol and luteolin. The HKUST-1 derived CuO NNs were employed as luminophore for the first time, which were successfully fabricated by using HKUST-1 as precursor. The results revealed that the HKUST-1 derived CuO NNs exhibit excellent ECL activity ascribed to its abundant active site and the high specific surface area, thus obviously promoting the separation and transfer of charge and further improving the current density of ECL sensor. To binary-amplify the signal of the ECL sensor, the AuNPs and TiO2 nano-materials with good biocompatibility, great electron transport efficiency and high catalytic activity were used as co-reaction accelerators in the ECL process. Dependent on the above brilliant strategy, the proposed ECL sensor achieved wide linear ranges from 3 × 10−9 – 1 × 10−4 M for catechol and 1 × 10−8 – 2 × 10−4 M for luteolin, with the detection limits of 1.5 × 10−9 M for catechol and 5.3 × 10−9 M for luteolin, respectively. Furthermore, the ECL sensor exhibited outstanding selectivity, repeatability, stability and obtained great feedback on determination of catechol and luteolin in actual samples. The method not only filled a gap in the ECL application of MOF-derived materials but also provided a novel sight for design other highly efficient luminescent materials.

In-situ synthesized MgIn2S4/CdWO4 type-II heterojunction as a light-driven photoelectrochemical sensor for ultrasensitive detection of catechol in environmental water samples

As an essential chemical intermediate, catechol (CC) residues may have adverse effects on human health. Herein, an effective and facile photoelectrochemical sensor platform based on MgIn2S4/CdWO4 composite is constructed for monitoring CC. MgIn2S4 increases light absorption range and activity, while CdWO4 enhances photoelectronic stability, and the type-II heterojunction formed can significantly enhance photocurrent response. Due to the autoxidation process, CC is converted into oligomeric products, which increase the spatial site resistance and attenuate the overall photocurrent response. It is worth noting that the cauliflower-like structure of MgIn2S4 can provide a large specific surface area, and the presence of Mg2+ promotes autoxidation, thus providing a suitable condition for detecting CC. Under optimal conditions, the MgIn2S4/CdWO4/GCE photoelectrochemical sensor has a prominent linear relationship in the range of CC concentration from 2 nM to 7 μM, with a limit of detection of 0.27 nM. With satisfactory selectivity, excellent stability, and remarkable reproducibility, this sensor provides a crucial reference value for effectively and rapidly detecting pollutants in environmental water samples.

Waste hazelnut shell based effective hydrothermal carbon/SnO2 nanoparticles: Towards electrochemical sensing of catechol in green tea, fruit juice, and urine samples

This study focused on the electrochemical detection of catechol (CC), a carcinogenic for humans and a periodic environmental pollutant found in consumed food and beverages and has low degradability and high toxicity in the ecological environment. Also, in this study, for the first time, a new and green electrochemical detection platform was developed for the detection of CC through green carbon material (HZ) recycled from waste hazelnut shells with the hydrothermal carbonization technique (HTC) and SnO2 nanoparticles (NPs). The morphology, surface chemistry, chemical structure, and physicochemical properties of the synthesized green-based functional carbon material and SnO2 NPs were thoroughly investigated and elucidated using different characterization techniques. Thus, a green perspective was contributed to the studies of researchers working on CC detection in designing new types of nanosensors and developing electrode modifications. On GCE with an HZ-SnO2 modification, the effects of pH, the supporting electrolyte, and the scan rate on the electrochemical behavior of CC were investigated. The limit of detection (LOD) of the proposed nanosensor for CC was determined as 8.51 nM and the linearity range was determined as 0.80–80 µM under optimal conditions using adsorptive stripping differential pulse voltammetry (AdsDPV).The developed new type, the green method, has been performed to detect the CC in green tea, fruit juice, and urine samples with sufficient accuracy and precision.

Electrochemiluminescence detection of catechol and tryptophol using nitrogen, sulfur co-doped graphene quantum dots based on a paper-based sensor

In this study, Nitrogen and Sulfur co-doped Graphene Quantum Dots (N, S-GQDs) were synthesized via a pyrolysis approach, utilizing citric acid as the carbon source and L-cysteine as the nitrogen and sulfur sources. These N, S-GQDs were used to develop a novel paper-based electrochemiluminescence (ECL) sensor for the detection of catechol (CC) and tryptophol, two potentially hazardous substances in the environment. Screen printing technology was utilized to construct the ECL sensor on filter paper, incorporating a hydrophobic layer, working and counter electrodes, and a reference electrode. The presence of CC and tryptophol was found to result in a decrease in the ECL intensity of the quantum dots (QDs), this quenching phenomenon is attributed to the oxidation of these substances within the electrochemical system and the subsequent electron transfer from the excited state of the QDs to the oxidation products. The sensor demonstrated a linear detection range for CC and tryptophol from 0.01 to 1000 μM, with detection limits of 0.0082 μM and 0.0066 μM, respectively, and exhibited excellent selectivity, stability, and repeatability. This cost-effective and efficient monitoring technique holds significant promise for environmental and health safety by facilitating the detection of CC and tryptophol, thereby mitigating their potential adverse impacts.

Facile synthesis of CeO2·CuO-decorated biomass-derived carbon nanocomposite for sensitive detection of catechol by electrochemical technique

Catechol (CC) is renowned for its ability to interact with a wide range of biomolecules, a trait that raises potential health concerns. Consequently, herein we achieved a significant milestone by developing an electrochemical CC sensor with improved performance such as exceptional sensitivity and selectivity. In this CC sensor we used Cerium (IV) oxide-doped Copper (II) oxide decorated biomass-derived carbon (BC) nanocomposite, known as CeO2·CuO@BC as the sensing material. This material has been artfully integrated into the modification of a glassy carbon electrode (GCE), showcasing the synergy of advanced materials and electrode design. The efficacy of the CeO2·CuO@BC nanocomposite as a sensing material underwent rigorous evaluation through comprehensive characterization techniques such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectrum, Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and Energy-Dispersive X-ray Spectroscopy (EDS). As a result, we developed a sensor that can quantify CC concentrations across an extensive dynamic range, spanning from 0.5 μM to a remarkable 8470 μM in a neutral phosphate buffer solution. This sensor, boasting a sensitivity of 0.4171 μAμM−1cm−2, coupled with an impressive detection limit of a mere 0.035 μM, stands as a testament to its superior performance. Its exceptional sensitivity and selectivity allow precise catechol level detection in real-world samples, making it invaluable for analytical applications. Beyond its analytical prowess, the sensor demonstrates remarkable durability through excellent reproducibility, repeatability, and stability. This robustness underscores its reliability, establishing it as an indispensable and highly efficient electrode for accurate CC determination across various practical scenarios.

Porphyrin-based covalent organic framework integrated with nitrogen doped carbon nanotube as electrode modifier for selective and simultaneous detection of hydroquinone and catechol with high sensitivity

A novel Co-porphyrin-based covalent organic framework (TT-COF(Co)) was synthesized and further integrated with nitrogen doped carbon nanotube (N-CNTs), which was used as electrode modifier material for the application in selective and simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CA). The successful formation of TT-COF(Co)/N-CNTs nanocomposite was confirmed through a series of different characterization techniques, including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Electrochemical results indicated that TT-COF(Co)/N-CNTs nanocomposite modified electrode had excellent sensing performance for HQ and CA in phosphate buffer, enabling selectively and simultaneously determination of these two dihydroxybenzene isomers. Under optimal testing conditions, linear calibration curves for the selective determination of HQ or CA in the presence of 30 µM of the corresponding isomers were obtained over the concentration range of 0.01–500 µM. The linear ranges for the simultaneous determination of HQ and CA were 0.003–300 µM, with detection limits of 0.81 nM for HQ and 0.74 nM for CA, respectively. The sensor also demonstrated satisfactory selectivity and stability, and was successfully used to analyse HQ and CA in real water samples. Our work made a useful contribution to strategical design of functionalized COFs materials for electrochemical sensing applications.